This is my first instructable, so I hope it is worthwhile.

I have a number of rotary tools that I use all the time. I wanted a quick method of securing them so my hands were free to hold the work, and a method of setting the height for cutting operations.
However, being broke it had to be very cheap, very simple and very quick to make using only the rotary tool and some other readily available tools, like a ruler and a cordless drill.

Step 1: Materials

The materials required are:

A base (I'd recommend using 3/4 or 15mm MDF, plywood or similar).
4 off 100mm (4 inch) M6 (1/4 inch) bolts
4 off 'Nylock' nuts to suit the above
8 off standard nuts for same
16 washers for same

An emergency pipe repair kit.

Depending on the pipe repair kit, you should be able to mount a rotary tool up to 2 inches diameter across the body, as long as it does not have too many compound curves. I doubt it will work with the very 'ergonomic' designs.

I was using it for a MiniCraft Drill and the Extension shaft drive of an El Cheapo tool.
The pipe repair kit consists of two pressed steel plates, two strips of dense rubber and 4 nuts and bolts.

Step 2: Preparing the Pipe Kit

I got the pipe kit at a local hardware store on special offer for £3.00 GBP (about 5 bucks).

I discarded the nuts and bolts which went into the 6M jar for some other project.
I offered the plates up to the MiniCraft Drill, but they were a bit too long for the small body of the drill.
I cut the end off using the Mini Drill and some grinding disks (it used up one disk for each end, tough steel!).

I then trimmed the rubber to fit.

Step 3: Attach the Rubber

Next I used impact adhesive to glue the rubber to the plates. This will stop them from moving too much under pressure and ensure that they are correctly positioned to protect the drill body.

Step 4: Measuring Up

This stage is critical if we want any sort of approximate accuracy to the finished mount.

Find four plain nuts and bolts that will fit the plates. They should all be the same length. You can use the 100mm ones if you have nothing else, it will just mean a lot of nut spinning!

Using only hand tightness adjust the nuts until the drill is gripped solidly (no spanners yet please!).
Try and get the nuts on all four sides as equal as possible. You can do this by counting the number of threads above the nuts.

I used some cap head bolts about the right length for this. Now carefully measure the distances between the upper and lower points as close to the bolts as you can. Use a well marked ruler to do this.

If the gaps are all roughly the same (say within a millimetre or so of each other), write down the four gap sizes. If they are VERY different (say more than two millimetres out), try loosening and tightening various nuts and bolts until they are closer to each other. Use hand tension only.

Once you have a set of measurements, check that the drill seems tight in the plates but is free to spin and isn't in any sort of major stress.
If everything seems OK, take the SMALLEST measurement you recorded and round it down to the nearest millimetre. therefore if the measurement was 20.75, round it down to 20. Don't round up, and if it's an exact measurement, knock half a millimetre off.

Step 5: Support Pillars

The next step is the only only one that needs good (ish) accuracy. We need to make four pillars that will slide over the bolts between the plates. These need to be the length we just calculated, and as perpendicular at the ends as you can manage. They will act as protection so that we can't over-tighten the nuts and damage the drill. They will also act as a fixed spacer so that we can adjust the height of the mount with a fair degree of accuracy.

The pillars can be made of anything that will resist crushing along their length. Brass tube is a good choice, aluminium or steel would be better. One of the hard nylons (like Delrin) or ABS tube as long as the wall is thick enough. For this Instructable I have used thick walled PVC plumbing pipe, but you could use micro-bore copper or even 15mm (1/2 inch) copper pipe.
I used the rotary tool to cut these but if you are using metal pipe and have a pipe cutter it should make the job easier.

The key is to try and get them all the same length and nice and flat at the ends.

Step 6: Assemble and Test

Fit the support columns, tighten them up with a spanner. Go GENTLY to make sure that the drill is not harmed. If you cut them too short you risk cracking the plastic body of the drill. Once they are reasonably tight run up the drill. Make sure that it turns freely but won't move in the mount.
Nip the bolts up another quarter turn and retest.

If everything turns as it should and there's no complaining from the drill then it should be fine. This also means that when fitting the drill into the mount in future you can simply tighten up the nuts in the knowledge that the pillars will set the correct size to hold the drill.

If you have more than one rotary tool of differing diameters, you will need to make a set of pillars for each one.

Step 7: Making the Base

Here I've used a piece of 1/4 inch MDF because it was all I had to hand for this instructable. I'd recommend using 15mm or 3/4 inch material for a really strong base.

Strip the mount back down and put the bolts you used to test fit back into stock. Cut your base to the size you want remembering to leave room in front of the mount for working. carefully measure the hole locations on the lower plate. Mine were 38mm apart lengthwise and 42mm apart across the plate.

Mark up the base using these dimensions. I strongly recommend that you start with a centreline as I have done and work from that. It will be very difficult to adjust lateral errors at this stage so be as accurate as you can.

Drill the four locating holes to suit your bolts. try and keep the holes as perpendicular as you can. If you have access to a drill press use that, but I did these with a cordless drill by eye.
You will need to fit rubber feet, or recess the back for the bolt heads or use some other method to raise the baseboard to clear the bolt heads.

Step 8: Assembling the Base

Take your 4 long bolts (I used threaded stock cut to size with Nylock nuts) and place a washer on each. Pass them up through the base board and place another washer on top. Add four standard nuts to the top and fully tighten them down. These are your support posts.

Add four Nylock nuts and screw then down until they are 10mm clear of the base nuts. Place a washer on each. Then add the lower plate, the fours pillars, the upper plate, four washers and four plain nuts.

Step 9: Set Up and Adjustments

Fit the drill and tighten down the nuts.

Chuck a piece of straight rod, hopefully it will align with your centreline. There is very little available lateral adjustment.
Using a ruler, measure the height of the rod above the base near the chuck. Now measure at the end of the rod. If the rod is lower at the end furthest from the chuck, then adjust the two rear posts of the mount by dropping the rear mount, lower Nylock nuts by half a turn and screwing down the rear upper nuts by half a turn. You get the idea.

Once the rod is level all along it's length then the drill is level and true.
Raising and lowering the drill above the base is simply a matter of raising or lowering all four posts.
If you used M6 bolts for this then one full turn of the nuts will raise or lower the drill by exactly 1mm.

Now add the tool of your choice to use the mount as a grinder, slitting saw, cutter, planer etc.
Add simple fences with clamps or more complex mounts to sand and grind parallel, or cut strips etc.

Simple and effective. If set up correctly you can even do simple surface grinding with this thing.